A desktop computer installation typically has associated with it a number of peripheral devices and other associated electrical devices, each of which is separately electrically powered. The peripheral devices can include such things as printers, scanners and modems or there may be associated devices such as a desk lamp or a room heater.
These peripheral devices and associated electrical equipment are in general not used when the computer is not in use. However, because they are separately electrically powered the user must, when turning off the computer, also turn off each of the peripheral and associated devices. This is a time consuming process and indeed given the placement of the power switches on many such electrical devices, may be extremely inconvenient.
It is also the case that widely used computer operating systems require significant time to perform certain “housekeeping” tasks in between receiving command to shut down and actually shutting off the power or being in a position to have the power supply to the computer shut off without causing problems for the computer system. During this time, the computer system also may not tolerate having power removed from peripheral devices.
Accordingly many users simply leave the additional devices powered on after the computer has been shut down.
This is not ideal for a number of reasons. The first of these is that the devices continue to consume power which is both costly and a waste of resources. This is particularly a problem since many modern devices use small plug-in transformers to provide the lower operating voltages which they require. These plug-in transformers continue to consume power whilst they are connected to a mains supply even if the power switch on the device which they are supplying with power has been switched off. Newer power supplies use solid state switching devices but still consume about 0.5 W.
It is also the case that all electrical devices have a finite life span of operation and this life span can be made to extend over a longer period of time if the device is switched off when not in use.
It is also advantageous that mains power be removed from devices when not required in order to reduce the possibility of exposure to damaging surges in the mains power supply.
Prior art devices have attempted to deal with this problem by providing relays which cut off power to peripheral devices when no current is flowing to the main device, the main device being the desktop computer itself.
However, most modern desktop computers have the ability to control their power usage to some extent by entering one or more lower power consumption states, usually referred to as standby states. Users may allow the device to spend extended periods in such a standby state, negating most of the advantages of the prior art devices.